Stroika

Stroika is a class library developed and rewritten nearly a dozen times over
the course of more than 5 years, to provide a complete, cross-platform C++
application framework. In its many incarnations, it has been ported to
MS-Windows, the Macintosh, and X-Windows/UNIX. It contains an underlying
foundation class library which is quite elaborate, and the best maintained
portion of Stroika.

Stroika is no longer maintained, and the source code is freely available for you to use.